Field of the Invention
This invention relates generally barrier layers and more specifically to barrier layers in pneumatic tires that decrease the diffusion of gas through the tire.
Description of the Related Art
Various articles are constructed to hold gas, such as air, under pressure, examples of which include tires, athletic balls such as basketballs, footballs and tennis balls, inflatable boats, air mattresses, and the like. These articles are typically made from a polymeric material having some elastic properties. Tires, for instance, are typically made from rubber materials such as styrene butadiene rubber, polybutadiene rubber and/or natural rubber.
Many elastomeric materials used to make inflatable articles may, in some circumstances, remain slightly permeable to gases. If left unchecked, the gas permeability of the inflated article may compromise the performance of the article and cause the article to deflate over time. Furthermore, if the gas that passes through the slightly permeable material is oxygen, then the oxygen can cause oxidation of the elastomers, causing deleterious effects to the properties of the elastomer, e.g., the elastomers may tend to harden and degrade.
In view of the above, it is often advantageous for inflatable articles to contain a barrier layer that reduces gas permeability and inhibits oxygen travel through the article. Often, in the past, these barrier layers have been made from a composition containing butyl rubber, a copolymer that contains a majority of isobutylene units. Butyl rubber in its raw state, however, still remains somewhat gas permeable. Thus, efforts continue in the industry to discover new ways of providing an effective barrier to the diffusion of gas through rubber articles.